1. The Field of the Invention
This invention is in the field of instruments for use in medicine and dentistry. More specifically, this invention is in the field of endodontic instruments for treating root canals as part of a root canal procedure.
2. The Relevant Technology
To preserve a tooth that has a diseased pulp cavity, it is necessary to prevent bacterial proliferation within the pulp canal of the tooth by removing the diseased or necrotic pulp material from the pulp canal. After the pulp material has been removed or extirpated from a tooth, the pulp cavity is typically filled or obturated with a material such as gutta percha to occlude the pulp cavity and a sealer to seal the pulp cavity. This procedure is referred to as root canal therapy. Root canal cleaning is generally achieved by hand or mechanical instrumentation with files that are configured to bore and cut.
It is also common during the root canal procedure to irrigate a pulp cavity and the various root canals involved using an endodontic irrigator tip. Irrigation assists in removing debris and necrotic material cut by the endodontic files and bores. Disinfecting solutions can also be employed in irrigation, thereby disinfecting the pulp cavity and root canals during the operative procedure.
Root canals are often thin, tight, twisted and cumbersome to negotiate. A major problem associated with negotiating such awkward spaces during root canal therapy is apical perforation, i.e., perforation of the apex of the root canal. Another problem involves failing to clean material close enough to the apex, thus leaving necrotic tissue within the root canal. Before instrumentation of a root canal, the length of the root canal is determined to identify a suitable working length for the file or irrigation tip. Generally, the working length corresponds to the distance from a fixed reference position on the crown of a tooth to the apex.
Radiography is the most common method for measuring the length of the root canal. A preoperative x-ray image of the diseased tooth is taken from the front or back of the tooth, as depicted in FIG. 1, to show a cross-sectional view of the root canals 12 of tooth 10. The length of the root canal and the desired working length of the file or irrigation tip to be placed therein are then estimated.
Apical perforations typically result from an error in estimating the length of a root canal or the working length of the file or irrigation tip. Perforation of the apex 14 of a root canal 12 can result from the use of files or endodontic irrigation tips which are too long. Similarly, apex 14 can be perforated by extrusion of infected material through the apex due to the force exerted by the file or tip on the material as the file or tip is pushed downward to reach the apex. In addition to exposing the tissue surrounding the tooth to the infected material, apical perforations also substantially complicate subsequent healing of the root canal.
The possibility of perforating the apex is particularly frustrating because it is often desirable to deliver fluid which reaches the apex in order to disinfect the apex and dissolve necrotic tissue therein. However, certain fluids are too viscous to reach the apex if delivered too far above the apex or may entrap air, which prevents the fluid from reaching the apex.
Incomplete removal of necrotic material can thus result from the failure of a dental tool to reach far enough into a root canal. In light of the desire to maneuver dental tools close to the apex without perforating the apex, practitioners have followed up the initial radiographic procedure described above by placing a radiopaque instrument into the root canal of an opened tooth, then making a radiographic image of the root canal with the radiopaque instrument disposed therein, e.g., by taking an x-ray. This follow up procedure radiographically records the position of the tip of the instrument with respect to the apex of the root canal. Based on the x-ray with the tool in the root canal, the practitioner is able to adjust the penetrating length of a file or other tool.
The radiographic tools of the prior art have typically been the cutting tools, e.g., files, employed by the dentist during cleaning of the root canal. However, such typical cutting tools, particularly the smaller diameter tools, often yield a low contrast between the tools and the tooth in which the tools have been placed. Such radiographic tools are typically extremely thin, having a circumference measuring in the thousandths of inches in some circumstances. Consequently, it is often very difficult to clearly see and determine apex proximity of such typical radiographic tools on an x-ray image. Such low contrast tools typically comprise, for example, stainless steel or nickel-titanium as the radiographic material. Sonic techniques and electrical convective techniques can also be used in addition to radiographic techniques, but they are not always entirely accurate.
There is therefore a need within the art for an improved endodontic marking instrument and a method for using the instrument.